#include <stdio.h>
#include <stdlib.h>
#include <inttypes.h>
#include <unistd.h>
#include <string.h>

#define abc 0
// #if abc == 1//条件成立编译
// #if abc//条件成立编译
#if abc > 0
int val1 = 1;
#else
int val1 = -1;
#endif

#ifdef abc//如果定义了abc，则编译。
int val2 = 2;
#else
int val2 = -2;
#endif

#ifndef defChk1
#define defChk1 1
#endif

#define defChk2 3
#ifdef defChk2
#undef defChk2
#define defChk2 4
#endif

int main(int argc, char **argv)
{
    printf("val1=%d,val2=%d\n", val1, val2);
    printf("def check1=%d,def check2=%d\n", defChk1, defChk2);
    return 1;
}
